Field of the Invention
The present invention relates to an image forming apparatus.
Description of the Related Art
In related art, an image forming apparatus that includes an image forming unit and a transfer unit and employs an electrophotographic system is known. The image forming unit forms a toner image on an image carrier, and the transfer unit transfers the toner image on the image carrier onto an intermediate transfer belt through primary transfer and transfers the intermediate toner image on the intermediate transfer belt onto a recording medium through secondary transfer (for example, see JP 2005-300615 A).
In a mechanism that performs the secondary transfer, the intermediate transfer belt and the recording medium are nipped so as to be in pressure contact with each other by a backup roller and a secondary transfer roller. The intermediate transfer belt is stretched over the backup roller, and the secondary transfer roller opposes the backup roller with the intermediate transfer belt interposed therebetween.
Normally, in such an image forming apparatus, the widths of the backup roller and the secondary transfer roller are fixed to widths larger than the maximum width of a recording medium that can be subjected to image formation.
Therefore, for example, in the case of using a recording medium of a small size, an area of rollers that comes into contact with the recording medium is small. In this case, although necessary control such as temperature control is only required to be performed on this area, an unnecessary area of the rollers is also controlled at the same time. This leads to a low productivity.
Moreover, for example, in the case of using a label paper sheet as the recording medium, glue is pushed out of an end portion of the label paper sheet by being nipped by the rollers and is attached to components that come into contact with the recording medium in the course of image formation. This causes malfunctions such as image defect and failure in sheet conveyance, and the glue requires to be cleaned. This leads to a low productivity.